The invention relates to a method for controlling a percussion device, the method comprising: providing impact pulses with the percussion device during drilling to a tool connectable to a rock-drilling machine; and generating a compression stress wave to the tool to propagate at a propagation velocity dependent on the tool material from a first end to a second end of the tool, with at least some of the compression stress reflecting back from the second end of the tool as a reflected wave that propagates toward the first end of the tool; and controlling the percussion device in the rock-drilling machine and its impact frequency.
The invention further relates to a software product for controlling percussion rock-drilling, the execution of which software product in a control unit controlling the rock drilling is arranged to perform at least the following action: to control the percussion device in the rock-drilling machine during drilling to provide impact pulses to a tool connectable to the rock-drilling machine, whereby a compression stress wave is arranged to form in the tool to propagate at a propagation velocity dependent on the tool material from a first end to a second end of the tool, with at least some of the compression stress reflecting back from the second end of the tool as a reflected wave that propagates toward the first end of the tool; and further to control the impact frequency of the percussion device.
The invention further relates to a percussion device that comprises: means for generating a impact pulse to a tool, whereby a compression stress wave caused by the impact pulse is arranged to propagate from a first end to a second end of the tool, and at least some of the compression stress reflects back from the second end of the tool as a reflected wave and propagates toward the first end of the tool; a control unit for controlling the impact frequency of the percussion device; and means for defining at least the impact frequency of the percussion device.
The invention further relates to a percussion device that comprises: means for generating a impact pulse to a tool, whereby a compression stress wave caused by the impact pulse is arranged to propagate from a first end to a second end of the tool, and at least some of the compression stress reflects back from the second end of the tool as a reflected wave and propagates toward the first end of the tool; means for controlling the impact frequency of the percussion device; and means for defining the impact frequency of the percussion device.
Percussive rock drilling uses a rock-drilling machine having at least a percussion device and a tool. The percussion device generates a compression stress wave that propagates through a shank to the tool and on to a drill bit at the outermost end of the tool. The compression stress wave propagates in the tool at a velocity that depends on the material of the tool. It is, thus, a propagating wave, the velocity of which in a tool made of steel, for instance, is 5,190 m/s. When the compression stress wave reaches the drill bit, it makes the drill bit penetrate the rock. However, it has been detected that 20 to 50% of the energy of the compression stress wave generated by the percussion device reflects back from the drill bit as a reflected wave that propagates in the tool into the reverse direction, i.e. toward the percussion device. Depending on the drilling situation, the reflected wave can comprise only a compression stress wave or a tensile stress wave. However, a reflected wave typically comprises both a tensile and a compression stress component. Today, the energy in the reflected waves cannot be efficiently utilized in drilling, which naturally reduces the efficiency of drilling. On the other hand, it is known that reflected waves cause problems to the durability of drilling equipment, for instance.